Solar pond powered liquid desiccant evaporative cooling

Liquid desiccant cooling systems (LDCS) are energy efficient means of providing cooling, especially when powered by low-grade thermal sources. In this paper, the underlying principles of operation of desiccant cooling systems are examined, and the main components (dehumidifier, evaporative cooler and regenerator) of the LDCS are reviewed. The evaporative cooler can take the form of direct, indirect or semi-indirect. Relative to the direct type, the indirect type is generally less effective. Nonetheless, a certain variant of the indirect type - namely dew-point evaporative cooler - is found to be the most effective amongst all. The dehumidifier and the regenerator can be of the same type of equipment: packed tower and falling film are popular choices, especially when fitted with an internal heat exchanger. The energy requirement of the regenerator can be supplied from solar thermal collectors, of which a solar pond is an interesting option especially when a large scale or storage capability is desired

Solar Powered Atmospheric Water Generation

Several atmospheric water generation (AWG) system configurations were analyzed to determine the feasibility of AWG as a method to combat water stress. In order to best combat water stress, AWG must be implemented in such a way which minimizes the energetic and monetary cost of water production. Thermodynamic and economic analyses were used to compare the performance of several AWG system configurations. Metrics such as specific energy consumption (SEC) and levelized cost of water (LCOW), which measure the energetic and monetary cost of water production respectively, were used to compare each system. Using this approach, the optimal system configuration was found to be a batch-style desiccant-based AWG system which utilizes latent energy recovery. The minimum theoretical SEC and LCOW for this system are 210 kWh/m3 and 3.34 $/m3 (12.64$/Kgal). A prototype of a batch-style desiccant-based AWG system with no energy recovery was developed and tested. The evaluation of this system validated the approach used in the thermodynamic analyses for predicting the system’s performance. Future work will involve implementing latent energy recovery and redesigning some of the system components in order to further decrease the system’s SEC

Sorption Water By Modified Bentonite

In order to improve adsorptive properties and provide a viable alternative to humidity control techniques, the desiccants can be modified with chemical aggregates such as calcium chloride (CaCl2), the latter often used as dehydrating due to its hygroscopicity and low cost. Its use as a drying agent has disadvantages because of its particles form a liquid film. However, the CaCl2 may be mixed with other materials for preparing desiccant products. In this work we studied, at 298 K and different relative humidities (RH), the adsorption processes of desiccants mixtures composed of a bentonite clay Argentinian and CaCl2. The results showed a better performance of the desiccant mixture with respect to natural clay in the whole HR working range. It was also observed that addition of CaCl2 favors adsorptive properties with respect to a purification treatment.Fil: Castrillo, Natalia Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones para la Industria Química; Argentina. Universidad Catolica de Salta. Consejo de Investigaciones; ArgentinaFil: Mercado, Adela Isabel Guadalupe. Universidad Catolica de Salta. Consejo de Investigaciones; Argentina. Universidad Nacional de Salta. Facultad de Ciencias Exactas; ArgentinaFil: Volzone, Cristina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentin

A techno-economic investigation of conventional and innovative desiccant solutions based on moisture sorption analysis

Liquid desiccant technology is an energy-efficient substitute for technologies that are conventionally applied for temperature and humidity control; however, innovative desiccant solutions have not been extensively explored in terms of their performance and feasibility. This work aimed to investigate desiccant solutions with moisture sorption analysis technically and economically. Various conditions of temperature and humidity were tested in a climatic chamber and the moisture absorption and desorption capacity, thermo-chemical energy storage capacity, and cost of conventional and innovative desiccant solutions were assessed by experiment. Calcium chloride showed the highest moisture desorption capacity (0.3113 gH2O/gsol in the climatic chamber at 50 °C and 25% RH) and the lowest cost, despite its low moisture absorption capacity. Ionic liquids show high moisture absorption capacity (as high as 0.429 gH2O/gsol in the climatic chamber at 25 °C and 90% RH) and could be used as additives (in which a maximum increase of 84.1% was observed for moisture absorption capacity due to the addition of ionic liquids), and thus, they are promising substitutes for conventional desiccant solutions. As solutions for better performance under various conditions were identified, the study will advance liquid desiccant technology

Performance assessment of a membrane liquid desiccant dehumidification cooling system based on experimental investigations

A membrane-based liquid desiccant dehumidification cooling system is studied in this paper for energy efficient air conditioning with independent temperature and humidity controls. The system mainly consists of a dehumidifier, a regenerator, an evaporative cooler and an air-to-air heat exchanger. Its feasibility in the hot and humid region is assessed with calcium chloride solution, and the influences of operating variables on the dehumidifier, regenerator, evaporative cooler and overall system performances are investigated through experimental work. The experimental results indicate that the inlet air condition greatly affects the dehumidification and regeneration performances. The system regeneration temperature should be controlled appropriately for a high energy efficiency based on the operative solution concentration ratio. It is worth noting that the solution concentration ratio plays a considerable role in the system performance. The higher the solution concentration ratio, the better the dehumidification performance. However simultaneously more thermal input power is required for the solution regeneration, and a crystallization risk in the normal operating temperature range should be noted as well. The system mass balance between the dehumidifier and regenerator is crucial for the system steady operation. Under the investigated steady operating condition, the supply air temperature of 20.4°C and system COP of 0.70 are achieved at a solution concentration ratio of 36%

Modelling and experimental verification of a solar-powered liquid desiccant cooling system for greenhouse food production in hot climates

Experiments and theoretical modelling have been carried out to predict the performance of a solar-powered liquid desiccant cooling system for greenhouses. We have tested two components of the system in the laboratory using MgCl2 desiccant: (i) a regenerator which was tested under a solar simulator and (ii) a desiccator which was installed in a test duct. Theoretical models have been developed for both regenerator and desiccator and gave good agreement with the experiments. The verified computer model is used to predict the performance of the whole system during the hot summer months in Mumbai, Chittagong, Muscat, Messina and Havana. Taking examples of temperate, sub-tropical, tropical and heat-tolerant tropical crops (lettuce, soya bean, tomato and cucumber respectively) we estimate the extensions in growing seasons enabled by the system. Compared to conventional evaporative cooling, the desiccant system lowers average daily maximum temperatures in the hot season by 5.5-7.5 °C, sufficient to maintain viable growing conditions for lettuce throughout the year. In the case of tomato, cucumber and soya bean the system enables optimal cultivation through most summer months. It is concluded that the concept is technically viable and deserves testing by means of a pilot installation at an appropriate location

Sorption Water By Modified Bentonite

In order to improve adsorptive properties and provide a viable alternative to humidity control techniques, the desiccants can be modified with chemical aggregates such as calcium chloride (CaCl2), the latter often used as dehydrating due to its hygroscopicity and low cost. Its use as a drying agent has disadvantages because of its particles form a liquid film. However, the CaCl2 may be mixed with other materials for preparing desiccant products. In this work we studied, at 298 K and different relative humidities (RH), the adsorption processes of desiccants mixtures composed of a bentonite clay Argentinian and CaCl2. The results showed a better performance of the desiccant mixture with respect to natural clay in the whole HR working range. It was also observed that addition of CaCl2 favors adsorptive properties with respect to a purification treatment.Centro de Tecnología de Recursos Minerales y Cerámic